SDIA definition
SDIA will often refer to Big Tech as the major foreign cloud service providers that dominate market share through economies of scale and vertical integration; namely, Alphabet (Google), Amazon, Alibaba and Microsoft. It further refers to digital product & service companies which have a significant market share in their respective category, for example Tencent or Facebook.
Other definitions
Big Tech is widely defined as the most prosperous and influential technological companies in in the IT industry. They are often called the Big Five and include the following U.S. companies: Alphabet (Google), Apple, Meta, Amazon and Microsoft.